Justin Kavanaugh remembers the first time he visited the hulking building set amid the strip malls of Chantilly, Va. He walked around the trio of turf fields, the weight room, the group exercise studio and the massive basketball court. And he was awfully confused.

“I thought this was a church,” Kavanaugh says. “I was looking for stained-glass windows.”

Instead, he found himself in the nZone, an 83,000-square-foot athletic training facility that offers fitness classes, youth programs, leagues and — since shortly after that visit — specialized courses with Kavanaugh’s Sport and Speed Institute.

The only overt sign that there’s anything religious about the place? A few banners touting the New Life Christian Church, which runs the nZone as a nonprofit organization.

“Fairfax County (Va.) is not the Bible Belt. This is an area where churches haven’t necessarily been perceived as good things,” says pastor Brett Andrews, who founded New Life two decades ago. So when his congregation finally secured the funds to buy a building, he was determined not to put up a typical church.

Dropping $10 million on a place that would sit empty most of the week didn’t make sense, Andrews says. And when New Life solicited advice on what folks in the area could use, the same response kept coming up: “We need more stuff to get kids off the street.” That’s why the nZone opened two years ago in a former Anheuser-Busch distribution plant.

It’s not unknown for a church (or synagogue or mosque) to take an interest in physical fitness; some have some sort of recreation room on site, often reserved for members of the congregation. But this is a full-on recreation center, without a single space built specifically for worship. And the vast majority of people taking advantage of the facility have no connection to the church.

The external focus makes the situation even more unusual, explains Phil Ling, who runs a national church consulting firm. He has worked with congregations across the country and has never seen anything quite like the nZone. “It’s one thing to reach out,” Ling says. “It’s another to build a state-of-the-art athletic training facility for thousands of people.”

To Andrews, it’s a chance “to show the love of God in a practical way.” And it’s an opportunity to connect with a wider swath of society. Ron Furgerson, a member of the church leadership team, recalls that there was some concern when the nZone was approached by a group that wanted to host a mixed martial arts tournament there.

The fears — “Will there be blood spilled? Is that the sort of thing a church can sponsor?” — were outweighed by the appeal of bringing in potential attendees. “It’s almost a sin to have a building the community can’t use,” says Furgerson, who notes that the nZone has now hosted several MMA nights. (There are two rules: The ring girls have to be “appropriately attired” and there’s no alcohol.)

Although the nZone staff takes pains not to proselytize, there is a religious fervor to how they approach their mission. Anyone who walks in should get more than a workout, explains Creed Branson, who’s both New Life’s executive minister and president of the nZone. “We want them to experience God,” he says.

There’s a stock answer prepared for how exactly they can pull that off: “By providing the best customer service in Northern Virginia.” That seems to translate into beaming smiles, frequent handshakes and bargain prices. An nZone fitness membership — which includes access to the facilities and more than two dozen classes a week — is just $25 a month.

Whatever the nZone is doing is working for retired Washington Redskins star Darrell Green, who regularly plays basketball there with a group of guys. “They let me score a point every once in a while,” the 53-year-old Hall of Famer jokes. Green belongs to a church about a mile away, but he feels just as welcome when he enters the nZone.

“There are no requirements,” Green says. “The environment is so safe, healthy and encouraging — I wish we had one in every neighborhood and community.”

It was this vibe that first brought Morris Zamora, 49, through the doors. The Chantilly resident coaches children’s soccer, and the nZone offered a free place for his team to host a party at the end of the season. After having a positive experience and hearing raves from relatives about the gym, Zamora decided to give religious services a try, too. His family has been coming for a little over a year.

“The kids love it. We have to drag them out of here,” he said on a recent Sunday, pointing to the turf field where youngsters have an abbreviated service and then can run around.

That morning, Zamora and hundreds of other churchgoers paraded onto the basketball courts, which are transformed every weekend with giant carpet squares and comfy chairs. Mostly young families in sneakers and sweats filtered into the cavernous room that was pitch dark, except in one corner, where a band rocked out onstage. Behind them were three huge screens, flashing the lyrics to their songs.

After the opening act, Andrews bounded up in jeans and a green henley, and launched into a sermon about baptism.

Each week, when Service No. 3 is finished, the church supplies are swiftly stacked up and rolled away, and the nZone is back in business. By the following day, it’s tough to imagine the place as anything other than an athletic facility.

Near the entrance, Kavanaugh is huddled around a cafe table, discussing the NFL prospects of two of his top athletes with their parents. Every inch of turf is being used: Some teenage boys are stretching in a corner while younger girls have a soccer lesson, and a father and son toss a football.

Adults are sweating through a set of pushups in the group exercise studio, which is called the Keg Room as a nod to its previous incarnation back in the beer distribution days. (“Go in with a keg, leave with a six-pack,” cheers the nZone’s Nicole Strohl as she passes by.)

Other folks are running on treadmills, taking martial arts classes and practicing their dribbling skills. It’s all ages, and a whole lot of energy.

One of the few church members around is David Edwards, 43, whose son is in a basketball program. He admits that he was skeptical when he heard about plans for the nZone. “I was a little like, ‘We’re not going to build a church?’ ” he says. But now when he mentions the nZone to his neighbors, he’s proud to hear they’ve come for boot camps, volleyball games or birthday parties.

The church affiliation is part of the appeal for several visitors, including Alvin Martin, 48, who regularly makes the trek from Stafford, Va., with his 10-year-old son, also named Alvin. They ended up here after an Internet search for indoor athletic facilities, and they didn’t have a clue about the New Life connection until they explored the place. But he likes the effect it has. “I don’t see a lot of negativity. No one is yelling and cursing,” Martin says.

For the most part, the draw seems to be the resources, the reasonable prices and the variety of programming.

“This provides everything I need,” says Brenda McEwen, 60, as she puts away dumbbells after a class. The Centreville, Va., resident has been a fitness member since February, and she says she’s never felt pressured to do anything that made her uneasy. “At some places, you get stuff shoved down your throat. If you’re here, you can just work on your temple.”

When people feel that way, Andrews says, the nZone is working. And he’d like to see the model replicated. New Life has been exploring the possibility of opening a second location.

in Prince William County, near his home in Gainesville, Va. It’s just a matter of raising enough money - because, like stained-glass windows, indoor fitness facilities don’t come cheap.